Abrasive blast cleaning system

ABSTRACT

An abrasive blast cleaning system includes a pair of separators for separating sand from abrasive particles in conjunction with a no-bake molding procedure with crushing rollers being provided between the separators to crush small lumps of pea size sand.

United States Patent 1151 3,694,964 Bowling, Jr. 1451 Oct. 3, 1972 [54]ABRASIVE BLAST CLEANING SYSTEM 3,055,150 9/ 1962 Greenberg et al. ..5 H319 X 72 I t I h E. Bo Ii 3,097,450 Freeman fit 3.] X l 1 fiz w Jr3,097,451 7/1963 Freeman et al ..51/319 x 3,368,677 2/ l 968 Bradley..209/135 1 Asslgnee= h Carbonmdum Company, 3,540,156 11/1970 Stebbinset a1 ..51/320 x Niagara Falls, NY. 2,962,230 11/1960 Dilley ..24l/77 X22 i N 13 1970 2,996,261 8/ 1961 Picalarga ..241/77 [2]] 89181 PrimaryExaminer-Donald G. Kelly I AttomeyDavid E. Dougherty and Robert E.Walter [52] US. Cl ..51/9 51 Int. Cl ..B24c 3/08 ABSTRACT [58] Field ofSearch 3 2 5 An abrasive blast cleaning system includes a pair ofseparators for separating sand from abrasive particles in conjunctionwith a no-bake molding procedure with [56] References cued crushingrollers being provided between the separators UNITED STATES PATENTS tocrush small lumps of pea size sand.

1,954,111 4/1934 Wilks ..51/8 7 Claim, 2 Drawing figures ABRASIVE BLASTCLEANING SYSTEM BACKGROUND OF INVENTION A recent development in thecasting industry is the use of chemical bonded molds. Essentially thispractice utilizes quality sand, a chemical binder and a catalyst whichare mixed together and hardened into a solid cake at ambienttemperatures. Accordingly, baking is not required for such molds and thepractice is, therefore, known in the art as no-bake molding. Generallythe base binder used in no-bake molding is either an acid base such as achemical binder with phosphoric acid as the activator or is an oil base.In practice the nobake mold pattern is disposed in a topless frame on,for example a support table with the no-bake ingredients being added toform a cavity corresponding to one portion of the casting and withrigidifying rods added thereto. The mold is then inverted and thecomplementary portion of the no-bake mold is formed thereon so that theresultant composite cavity corresponds to the casting. Suitable gatingis of course also provided. This practice is generally similar tostandard foundry techniques but thus differs in at least one majorrespect, namely, the no-bake molding equipment does not require a heavyflask in which to house the sand when the molten metal is subsequentlyapplied to the cavity. Even the topless frame used initially in theprocess is not needed during the casting forming step.

The no-bake molding process potentially represents a significantadvancement in the foundry art since it offers a number of distinctadvantages. For example the molds are easier to make without requiring askilled molder. There is a cleaner environment with less dust andspillage than with green sand molding. The nobake technique is quickersince jolt mechanisms are not required. Simple form boxes or toplessframes are merely necessary to shape the mold rather than theconventional heavy flasks. The molds can be handled without breakingapart by providing a grid plate or strapping and thereby the mold withits casting can be moved to a shaker or cleaning process withoutbreaking apart. It has been suggested that the mold shell or sand can beremoved by blasting and in such case the mold shell and core can behandled to the interior of a blast machine where the sand and dust canbe contained and shakeout noise eliminated. Moreover, the casting finishis thereby improved and casting tolerances can be tightened with thecastings matching the pattern. The castings can go directly tonumerically controlled machines, thereby obviating the need for roughcuts on manual machines.

Despite, the numerous advantages such as indicated above which arepossible with no-bake molding, there are a number of seriousdisadvantages which might cause this process to meet stiff acceptance bythe foundry art. These disadvantages include the increased costs forquality grade sand which might cost three or four times more than thecost of green sands. Since quality sand is used this sand must bereclaimed for reuse to make the entire process economically feasible.

Although attempts are being made at reclaiming and reusing the sand,experts cannot agree on the percentage of reclaiming possible with asystem nor the qualities needed or obtained by a system. Thepublication, Foundry, September 1970, pages 8389, for example, describesone such attempt at sand reclamation. The

reclaimed sands with the present systems, however, are not uniform inqualities. In this respect the build-up of fines and/or organicsseriously affects the molds using reclaimed sands. Moreover, proposedreclaiming systems require shakers, crushers or Muller type units whichare noisy and dusty and also require rather large floor space and headroom with high maintenance and capital costs.

SUMMARY OF INVENTION An object of this invention is to provide anabrasive blasting system which includes means for effectively separatingsand from abrasive particles.

A further object of this invention is to provide such a system which isparticularly adapted to be used in con junction with the no-bake moldingprocess.

In accordance with this invention an abrasive blast cleaning systemincludes a pair of separators for separating sand from abrasiveparticles in conjunction with a no-bake molding procedure with crushingrollers being provided between the separators to crush small lumps ofpea size sand.

The separators may be of the air wash type which include skimmer platesfor dividing the mixture passed thereto into the individual streams. Thelowermost separator of each pair need only include one skimmer platesince the mixture passed through that separator contains only sand andabrasive particles. The crushing rollers may be made of a wear resistantmaterial such as polyurethane.

THE DRAWINGS FIG. 1 is a side elevation view schematically showing oneembodiment of this invention and FIG. 2 is a cross-sectional elevationview on an enlarged scale of a portion of the embodiment in FIG. 1.

DETAILED DESCRIPTION Recently filed application Ser. No. 108,417, filedJan. 21, 1971, in the names of James H. Carpenter and Joseph E. Bowling,Jr., is concerned with a comprehensive abrasive blast cleaning systemused in conjunction with the no-bake mold process. The system of thatapplication generally includes means for the granulation and scouring ofthe sand used in a no-bake mold for ultimate reuse of the sand. Inconjunction with that system separating means are disclosed foreffectively separating the granulated sand from abrasive particles. Thisapplication is concerned with a particular aspect of that system,namely, the means for assuring complete separation of the sand from theabrasive particles by the inclusion of crushing means between a pair ofair wash separators for crushing pea sized lumps of sand discharged fromthe first separator and prior to its passage into the second separator.

FIG. 1 illustrates the general arrangement of the system disclosed inthe copending application. As indicated therein a no-bake mold 12 isheld in an open frame 14 and conveyed on monorail 16 into blast chamber18. As is conventional with such no-bake molds rigidifying rods 20 aswell as a casting 22 are embedded in the sand 24. Means 26 are providedto suspend the casting when the sand is later removed.

Blast chamber 18 is provided with a plurality of centrifugal throwingwheels 28 which project abrasive particles against the mold to removethe sand and rods therefrom and thereby clean the then exposed castingin one operation. When the sand is removed from the mold it has beenfound that about percent of the sand is in lump form while the remaining75 percent is in granular form. The falling sand, rods, spent abrasive,fines and other contaminants fall through the bottom 30 of chamber 18and are received on oscillating conveyor 32. To facilitate the dischargeof this mixture of sand, abrasive, etc., from chamber 18 the floor ofthe chamber is made with maximal open area. Ideally chamber 18 would becompletely floorless. It is generally desired, however, to have somestructural members at the bottom of chamber 18 to permit workmen toenter for various purposes. Thus as shown in FIG. 1 spaced I-beams 34are provided so that the mixture 36 can be received on the oscillatingconveyor 32 by falling through the large open areas between I- beams 34.

The entire mixture 36 is conveyed on oscillating conveyor 32 until themixture reaches a portion of the conveyor which includes a screen 40 ofappropriate mesh size to permit the fine grain abrasives, fines, andother contaminants to fall into hopper 42 and thence to screw conveyor44 where it is received by elevator 46 for separation as laterdescribed. The remaining portion of mixture 36 which includes lumps,rods, and any other elements which may be carried with the mixture isconveyed to the end of oscillator 32 and drops onto generallyperpendicular oscillating conveyor 48 until it reaches the second blaststation 50.

Blast station 50 includes a conventional centrifugal throwing wheel 80which uses generally large size metal shot projected at a high flow rateat for example 1,200 to l700 rpm or lower. The metal shot strikes thelumps to granulate them while also knocking the organics off the grainsof sand. Advantageously the sand which had been separated by theseparators 54 and 68 (as later described) is also passed into the blaststream from wheel 80 so that the organic binder is removed from thissand. For example the falling sand from conduit 78 may drop between theblast stream from wheel 80 and a strike plate 84. In this manner theabrasive particles from a portion of the blast stream hit the fallingsand and causes the sand grains to strike each other and to ricochetagainst the strike plate 84. The resulting impacts effectively removethe organic binder. In the meantime the remaining portion of the .blaststream granulates and scours the lumps 86 and cleans the rods 20 whichare moving on oscillating conveyor 48. A portion of oscillating conveyor48 is provided with a screen deck of appropriate mesh size to permit thegranulated sand and abrasive particles to fall into hopper 89 to screwconveyor 90. The larger rods, however, continue to flow on oscillator 48and are ultimately discharged and collected in any suitable receptacle(not shown). Thus the rods are received from blast station 50 in acleaned condition for reuse.

From screw conveyor 90 the mixture of granulated reconditioned sand andabrasive particles are fed to elevator 92 and then to separator 94 whichalso is of the air wash type previously described including air curtaininlet 96 and skimmer plate 100 in separation chamber 98. The mixture isthereby divided into one stream of abrasive particles which is receivedin spout 102 and conveyed back to abrasive blast wheel 80 while thestream of reconditioned sand is received in spout 104 and dischargedfrom outlet 106 and into any suitable receptacle (not shown) for reuse.

Prior to discharge from outlet 106 the sand may pass through magneticdrum separator 107 to remove the small quantity of metal abrasive thatmay be mixed in with the otherwise substantially pure sand.

As previously described a portion of the mixture is received in elevator46. This portion is discharged into screw conveyor 52 and into anysuitable number of separators 54. FIG. 2 shows the details of thisportion of the arrangement, of which this invention is particularlyconcerned. As shown therein separators 54 are of the air wash type suchas described and illustrated in U. S. Pat. No. 3,368,677 the details ofwhich are incorporated herein by reference thereto. In general the airwash separator 54 subjects the falling mixture to an air curtainsupplied for example at inlet 55. Anumber of skimmer plates 58 areprovided in the separating chamber 60 to facilitate a separation ofthe'mixture into individual streams in accordance with their weight. Inthis respect the abrasive particles are heavier than the sand which inturn is heavier than the fines. Thus the abrasive particles fallgenerally directly downward into discharge conduit 62 while the timegrained sand is slightly diverted and received in discharge conduit 64.Discharge conduit 65 is provided for the fines and other contaminants,while dust in the air curtain exits through outlet 56 to a dustcollector (not shown).

It has been found that the sand in the mixture fed to separators 54 isnot always of the desired size of fineness but frequently is in smallerlumps 61 which may be termed pea size. Generally such pea sized lumpsare about 3/16 V4 inch in diameter. Since this pea size lumps of sand isheavier than the fine grain size lumps of, the pea size sand 61 willalso go into conduit 62 with the abrasive particles 63 which are largesize metal shot. Accordingly, it is necessary that this sand beseparated from the abrasive particles if the sand recovered is to bemaximized not only for reuse of the sand but also for reuse of theabrasive particles. Accordingly, the mixture of pea size lumps of sand61 and abrasive particles 63 undergoes a second separation process. Thissecond separation process includes feeding the mixture of abrasiveparticles and pea size lumps of sand through pairs of juxtaposed rollers66 which may be made of wear resistant polyurethane. The cylindricalrollers 66 may be mounted on shafts 77 in housing 67 at the mouth 69 ofspout 62. The closely positioned rotating rollers crush the pea sizelumps of sand 61 into its fine granular form 71 while of coursepermitting the abrasive particles 63 to retain their normal size. Thismixture of crushed sand and abrasive particles is then fed intoseparator 68 which is of the air wash type similar to separators 54except that only one skimmer plate is necessary since the mixture willbe divided into only two streams. Air is supplied through inlet 73 andis discharged along with any airborne contaminants through outlet 75.The substantially pure abrasive particles are received in spout 72 forreuse by blast wheels 28 by conveyance through pipes 74 (FIG. 1). Thefine grain sand is received in hopper 76 where it mixes with the finegrain flowing from conduits 64 and is conveyed through conduit 78 to theblast station 50 (FIG. 1).

What is claimed is:

1. An abrasive blast cleaning system comprising abrasive blast means forremoving a casting from a no bake mold and creating a mixture whichincludes fine granulated sand and pea size lumps of sand and abrasiveparticles, separating means, conveying means for transporting at least aportion of said mixture to said separating means, said separating meanscomprising a first separator for receiving the portion of said mixtureand separating it into individual streams which includes one stream ofabrasive particles and pea size lumps of sand, a second separator undersaid first separator, crushing means between said first separator andsaid second separator for granulating the pea size lumps of sand in theone stream and feeding the one stream to said second separator, and saidsecond separator separating the one stream into individual sub-streamsof abrasive particles and granulated sand.

2. The system of claim 1 wherein said crushing means includes a pair ofjuxtaposed rotatable rollers.

3. The system of claim 2 wherein each of said first and said secondseparators is an air wash separator with an air curtain inlet and an aircurtain outlet.

4. The system of claim 3 wherein said first separator includes aplurality of skimmer plates, and said second separator including asingle skimmer plate.

5. The system of claim 4 wherein each of said separators includesdischarge means for discharging a stream of granulated sand, and both ofsaid discharge means communicating with a common hopper.

6. The system of claim 5 wherein said rollers are made of wear resistantpolyurethane.

7. The system of claim 6 wherein said second Separator includes meansfor feeding its stream of abrasive particles to said abrasive blastmeans.

1. An abrasive blast cleaning system comprising abrasive blast means forremoving a casting from a no-bake mold and creating a mixture whichincludes fine granulated sand and pea size lumps of sand and abrasiveparticles, separating means, conveying means for transporting at least aportion of said mixture to said separating means, said separating meanscomprising a first separator for receiving the portion of said mixtureand separating it into individual streams which includes one stream ofabrasive particles and pea size lumps of sand, a second separator undersaid first separator, crushing means between said first separator andsaid second separator for granulating the pea size lumps of sand in theone stream and feeding the one stream to said second separator, and saidsecond separator separating the one stream into individual sub-streamsof abrasive particles and granulated sand.
 2. The system of claim 1wherein said crushing means includes a pair of juxtaposed rotatablerollers.
 3. The system of claim 2 wherein each of said first and saidsecond separators is an air wash separator with an air curtain inlet andan air curtain outlet.
 4. The system of claim 3 wherein said firstseparator includes a plurality of skimmer plates, and said secondseparator including a single skimmer plate.
 5. The system of claim 4wherein each of said separators includes discharge means for discharginga stream of granulated sand, and both of said discharge meanscommunicating with a common hopper.
 6. The system of claim 5 whereinsaid rollers are made of wear resistant polyurethane.
 7. The system ofclaim 6 wherein said second separator includes means for feeding itsstream of abrasive particles to said abrasive blast means.